Why not work under Linux keepalive

Testing found that after unplugging the network cable , if the socket has been attempting to receive , and does not transmit data, about 10 seconds to get a broken signal.
But if the socket has been sending data , the keepalive does not work, until the transmit buffer is full before disconnecting

 	int keepalive = 1; // 开启keepalive属性
 	int keepidle = 5; // 如该连接在5秒内没有任何数据往来,则进行探测
 	int keepinterval = 1; // 探测时发包的时间间隔为1 秒
 	int keepcount = 5; // 探测尝试的次数.如果第1次探测包就收到响应了,则后4次的不再发
 	socklen_t optlen = sizeof(socklen_t);
 	if (setsockopt(m_Socket, SOL_SOCKET, SO_KEEPALIVE, (void *)&keepalive, optlen) < 0 ||
 		setsockopt(m_Socket, SOL_TCP, TCP_KEEPIDLE, (void *)&keepidle, optlen) < 0 ||
 		setsockopt(m_Socket, SOL_TCP, TCP_KEEPINTVL, (void *)&keepinterval, optlen) < 0 ||
 		setsockopt(m_Socket, SOL_TCP, TCP_KEEPCNT, (void *)&keepcount, optlen) < 0)
 	{
 		ClosePort();
 		return false;
 	}
 

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according to your analysis of the phenomenon I feel like it works : If you do not set the keep alive, might you have in your socket ( obstructive ) above , the receiver : recv has been blocked can not be returned unless the peer closes a connection , because I do not know socket recv broken .
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enable this option to allow TCP connections on TCP socket send " keep alive " packets . Setting of this option value is stored in the transmission control block sk_flags of SOCK_KEEPOPEN bit , while according to the keep-alive function is enabled to determine whether to open the keep-alive timer .
keep-alive timer is selected in the application process SO_KEEPALIVE socket option is to take effect. If the connection is idle for more than 2 consecutive hours, the keep-alive timer expires, the connection sends a probe packet , forcing the responding .
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other comments you
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I encountered the same problem, Finally how LZ solution ?
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I have encountered similar problems , the landlord to solve it ?
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roof